Purpose: :
To study the correlation of objective and subjective measurementsof ocular discomfort.

Methods: :
27 participants were enrolled for the study. Soft (HEMA) contactlenses of eight different lens designs varying by base curveand diameter were fitted on all participants. The study wasconducted on two separate days with four lenses randomly assignedon each day. Subjective measurements of discomfort were obtainedusing numerical rating scales. The assigned contact lens wasfitted on one eye and the equivalent corneal discomfort wasmatched on the fellow eye using stimuli delivered from a computercontrolled pneumatic Belmonte esthesiometer. Corneal mechanicalthreshold was first measured using the ascending method of limitsand after contact lens insertion, the match of discomfort withcontact lens was set using the esthesiometer. Pearson productmoment correlation was used to correlate the objective esthesiometermatches to the subjective ratings of discomfort reported byeach participant.

Results: :
13 out of 27 participants showed statistically significant correlationbetween objective and subjective discomfort (correlation rangedfrom 0.71 to 0.89). The remaining subjects showed a correlationbetween -0.04 to 0.70, which were not statistically significant.In the group of participants that showed a good correlation,subjective discomfort ranged from 14.23± 12.39 to 59.23±26.99 for the most comfortable to the least comfortable lenswith corresponding esthesiometer values between 40.38±17.71 to 59.23± 26.99 ml/min. For the group with poorcorrelation, the subjective ratings were 21.43± 22.74to 56.43± 25.38 for the most comfortable to the leastcomfortable lens. The corresponding esthesiometer values were52.36± 25.78 to 56.43± 25.38 ml/min. The rangeof ethesiometer intensities used by the participants in poorlycorrelated group was insufficient to cover the subjective discomfortreported by them.

Conclusions: :
Subjective ratings of ocular discomfort can be scaled by cornealesthesiometry in a selective group of people. In the subsetof subjects with poorer correlations, perhaps the pneumaticmechanical stimulus was too localized and specific to matchthe complex sensations experienced while wearing contact lenses.Proper training in esthesiometry procedure might ensure a bettercorrelation. However, there is also a group of subjects whoare poor at making judgments about ocular comfort. So specialsensory panels should be used when ocular discomfort is theprimary outcome.